The pregnancy duration doesn't match.

I’m 10 weeks and 5 days pregnant according to my midwife today. My last menstrual period started on July 21. I have a cycle of 28 to 30 days. I tested positive on August 19 with a Clear Blue digital test. So I actually end up being 12 weeks and 1 day... If I’m currently 10 weeks and 5 days, that means I tested positive just a few days after conception. I think a difference of 1 week and 6 days is quite significant! Does anyone recognize this?